Single pile foot controller



June 7, 9 R. R. THOMPSON ET AL 3,323,740

SINGLE FILE FOOT CONTROLLER Filed Oct. 18, 1965 2 Sheets-Sheet l INVENTORS Ronald R. Thompson Alan H. Sfolpen BY W 3 ATTORNEY W WITNESS 7 June 27, 1967 R. R. THOMPSON ET AL 3,328,740

SINGLE FILE FOOT CONTROLLER Filed Oct. 18, 1965 2 Sheets-Sheet 2 I3 30 is o g \y 31 3 36} 34 20 s Y I5 v 24 43 INVENTORS Ronald R. Thompson WITNESS g 4 Alan H. Sfolpen BY 9' ATTORNEY United States Patent 3,328,740 SINGLE PILE FOOT CONTROLLER Ronald R. Thompson, Pluckemin, and Alan H. Stolpen, Union, N.J., assignors to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Oct. 18, 1965, Ser. No. 496,768 3 Claims. (Cl. 338-108) This invention relates generally to controllers for electric motor circuits and more particularly to controllers embodying carbon pile variable resistors for starting, stopping and controlling the speed of electric motors.

Controllers of this general type are particularly adapted for controlling electric sewing machine motors and are well known in the art as shown, described and claimed in United States Patents No. 2,371,772, granted to J. M. Naul on Mar. 20, 1945, No. 2,384,772, granted to C. R. Schenk on Sept. 11, 1945 and No. 2,536,012, granted to E. P. Turner on Dec. 26, 1950; all assigned to the same assignee as is the present application.

An object of the present invention is to provide an improved variable resistance controller of simple and rugged construction which is not readily subject to malfunction.

Another object of the present invention is to provide a controller with a carbon pile resistance element and a single leaf spring actuator for varying the resistance of the carbon pile as a function of deflection of the actuator.

Still another object of the present invention is to provide a controller with a carbon pile resistance element in fixed position therein and a single leaf spring actuator retained at its ends and having a transversely bent portion providing a pressure face deflectable for varying the pressure applied to the carbon pile for varying the resistance derived therefrom.

Another object of the present invention is to provide the foregoing controller in which the actuator thereof may be formed from a single sheet of metallic material or may be constructed from two pieces of standard strip stock.

The present invention contemplates a controller for electric motors, comprising a base, a carbon pile resistor connected to the base and supported thereby, a leaf spring actuator connected at its ends to the base and constructed to provide a transverse pressure face adjacent one end in contact with the carbon pile for applying pressure thereto, and means engaging the actuator intermediate the pressure face and the end opposite from such face for deflecting the actauto-r to vary the pressure applied thereto and the resistance derived therefrom.

The foregoing and other objects and advantages 'will appear more fully hereinafter from a consideration of the detailed description that follows, taken with the accompanying drawings wherein two embodiments are illustrated by way of example. It is to be expressly understood, however, that the drawirigs are for illustration purposes only and are not to be construed as defining the limits of the present invention.

FIGS. 1 and 2 are top plan and side elevation views,

respectively, of a controller made in accordance with the present invention, 1

FIG. 3 is an enlarged plan view of the novel controller of FIGS. 1 and 2 with the casing cover swung away to expose the component parts enclosed therein,

FIG. 4 is a longitudinal sectional view taken on line 4-4 of FIG. 3 with the casing cover disposed in its normal position for operation,

FIGS. 5 and 6 are lateral sectional views taken on lines 5-5 and 66, respectively, of FIG. 3 with the casing cover disposed in its normal position for operation,

3,328,740 Patented June 27, 1967 FIG. 7 is an enlarged fragmentary sectional view taken on line 7-7 of FIG. 3 illustrating a carbon pile pressure adjusting means,

FIG. 8 is a perspective view of the novel carbon pile pressure actuator, and

FIG. 9 is a perspective view of a modified form of the pressure actuator shown in FIG. 8.

Referring now to the drawings and particularly to FIGS. 1 and 2, a controller may have a casing comprising a hollow cover or foot pedal 10 pivotally connected along its rear edge to the rear edge of a hollow base 11 by a pair of spaced hinges as shown in FIG. 3. Cover 10 and base 11 are of a substantially rigid non-conductive or insulating material, such as a synthetic resin, and are prefer-ably molded to provide various mounting surfaces, recesses and protuberances required for installing various components, as hereinafter will be discussed. A controller casing of the above type is shown and described in a copending United States patent application Ser. No. 490,590, filed Sept. 27, 1965, and assigned to the same assignee as the present invention and to which reference may be had for a more complete understanding thereof.

As shown in FIG. 3, a variable resistance element 13 is disposed in the rear portion of base 11, being supported at its ends and clamped in position by a finger type sheet metal retainer 16 connected to the base 11 by a single threaded fastener. Resistance element 13 is preferably of the carbon pile type comprising a rigid insulating sleeve 14, of ceramic or other acceptable dielectric material, which houses a carbon disc pile 15.

As is also shown in FIG. 4, a pair of elongated leaf spring contacts 17 and 19 are disposed one above the other in base 11, forwardly of and substantially parallel to resistance element 13. Contact 17 is supported at its ends by base 11, and is provided with a terminal 18 at one of its supported ends. Contact 19, shorter than contact 17, is provided with a terminal 20 at one end and may be rolled at its other end 21. A block 22 is disposed between the terminal ends of contacts 17 and 19 for spacing the contacts and supporting the terminal end of contact 19. The rolled contact end 21 is disposed in spaced relation with and is free to move into and out of engagement with contact 17 when contact 19 is deflected. Contact 17 is supported at its free end by a boss 46 formed on the base 11. This double support for contact 17 enables it to exert a stronger pressure with less material than by other means and still permit over-travel of the cover 10 after full speed operation is reached.

A condenser 23, disposed in base 11 forwardly of the terminal ends of contacts 17 and 19, is connected to terminals 18 and 20 to absorb energy incident to sparking between all operating contacts and thus to reduce radiofrequency interference as is well known. A pair of insulated conductors 24 and 25, of a controlled motor circuit (not shown) enter base 11 through an elongated tubular'insulating grommet 26 and are connected to terminals 17 and 19, respectively, by-the respective terminals 18 and 20. Although terminals 18 and 20 are each shown as comprising a nut and bolt, in accordance with common practice, each such bolt may thre'adedly engage the associated contact.

It should be readily understood that contacts 17 and 19 provide a normally open circuit switch which is closed,

when maximum speed of the controlled motor (not single unit or as individual leaf spring elements. A pressure adjustment element 29 is threadedly supported by bracket 27 and has a U-spring portion 47 which engages the adjacent end of the carbon pile 15 to transmit pressure thereto and to complete an electric connection from resistance element 13 to conductor 24 through bracket 27 and terminal 18. Element 29 moves axially, when threaded into 27, to vary and adjust initial resilient pressure on carbon pile 15 to derive desired resistance from element 13 when the controller is in its unoperated condition and provides, through U-spring portion 47, means for compensating changing lengths of pile 15 due to heating and wear. It will also be noted that the U-spring 47 provides a resilient stop for the pile 15 which, for initial operational movement of the cover 10, effects a low rate of pressure buildup on the pile 15 which greatly improves the low speed control capability.

As shown in FIGS. 3, 4 and 8, a leaf spring type actuator 30 is provided in base 11 for varying pressure applied to the carbon disc pile 15 in response to movement or actuation of the cover or foot pedal 10. More specifically, actuator 30 is formed to provide a pressure face or portion 31 disposed across the end of element 13, opposite from adjustment element 29, and in contact with the carbon pile 15, Pressure face 31 has a flange 32 extending from its bottom edge that is connected to base 11, and an elongated spring leg 33 extending from its upper edge, substantially parallel to and offset from element 13, over contact 19 toward terminals 18 and 20. Thus, in effect, actuator 30 is merely an elongated leaf spring having an enlarged portion 31 adjacent one end and is formed or bent so the portion 31 is disposed in a transverse plane and offsets flange 32 from leg 33 along such transverse plane.

A block 35 is disposed between the end of leg 33 and the terminal end of contact 19 to space the free contact end 21 from leg 33. A threaded fastener 36 is provided to clamp, with blocks 22 and 35, the end of leg 33 and the terminal ends of contacts 17 and 19 to base 11. As shown in FIG. 4, blocks 22 and 35 are also insulators between leg 33 and contacts 17 and 19, and have keys extending through the said contacts to provide an interlock with base 11. One such key on each side of block 22 provides insulation for fastener 36 from contacts 17 and 19.

A flange 34 may be provided along the edges of the pressure face 31 between flange 32 and leg 33 for added rigidity, and another such flange may be provided at the end of leg 33 which extends into block 35 for positive interlock. It should be readily understood that leg 33 and contact 19 provide a normally open circuit switch in series with resistance element 13 to prevent unnecessary heating of the element 13 when the controller is unoperated and to disconnect electrically the controller from the electrical supply line as a safety feature.

It will be seen from FIG. 4 that block 35 is slidable to a degree with respect to block 22 and movement of block 35 compensates for linear and angular tolerance buildup and provides a coarse pile pressure adjustment.

A modified form of the actuator 30 of FIG. 8 is shown in FIG. 9. In this form the parts having similar function to those of FIG. 8 carry the same reference numbers. Referring to FIG. 9, it will be seen that the actuator 30 may be made in two parts 31 and 33, spot welded together and this may be desirable as a lower cost item since standard strip stock can be used in this form. Furthermore, the end of the leg 33 may be anchored to the block 35 by projections 50 formed in the block 35 and engaged by simple apertures made in the leg 33 as shown, If desired, a contact 51, preferably made of carbon, may be secured to the pressure portion 31 by a push nut, 52 pushed onto a reduced diameter thereof.

Cover or foot pedal has a pressure pad 37 which engages leg 33, intermediate its ends and above the free end 21 of contact 19. A spring 38 is provided in the front portion, at each end, of the casing for biasing the cover 10 to pivot away from base 11. The springs 38 are pressed over raised bosses 44 on the inner surface of the cover 10. The spring dimensions are such that the springs 38 hold themselves in place by helical contraction around the bosses 44 and are thus self-retaining. As the cover 10 is closed, the springs 38 are guided to their flat seats by the sides of conical recesses 45 formed in the base 11. As best seen in FIG. 5, such pivotal movement in response to the bias of springs 38 is limited by a self-locking screw 40 threadedly engaging an insert 41 in cover 10 and having a head engaged by a dished washer 39 movably disposed in a recessed opening in base 11. Cover 10 is adjusted to a desired unoperated position, by adjusting screw 40 to a position where pressure pad 37 deflects leg 33 to a predetermined gap distance from free end 21.

To prevent the controller from sliding when in use, cover 10 may have a plurality of parallel grooves 42 in its outer surface, and a friction pad 43 may be applied to the bottom surface of base 11.

In operation, downward pressure on cover 10 causes it to pivot on hinges 12 moving pressure pad 37 to deflect or bend leg 33 into engagement with the free end 21 of contact 19. This initial deflection of leg 33 establishes a closed resistance path between conductors 24 and 25 comprising terminal 18, leg 28 and bracket 27, pressure adjustment element 29, U-spring 47, resistance element 13, actuator 30, contact 19 and terminal 20.

As spring leg 33 is progressively deflected, by downward movement of pressure pad 37, the axial distance between its clamped end in block 35 and the pressure face 31 progressively shortens. This causes the pressure face 31 to move toward element 13 and exert progressively increasing pressure on carbon pile 15 for reducing the resistance thereof accordingly.

The characteristic of the pile resistance as a function of pile pressure is non-linear with the resistance change rate being large at low pressures and small at high pressures. The characteristic of the pile pressure as a function of cover movement is also non-linear with the pressure change rate being small at the beginning of cover movement and increasing with further cover movement. These two non-linear functions are mutually compensating, resulting in a substantially linear characteristic of resistance as a function of cover movement, which char- .acteristic is desirable for good motor speed control.

Contact 19 is common to both the resistance and bypass flow paths between conductors 24 and 25, and is deflected simultaneously with leg 33 when the resistance path is established. Leg 33 and contact 19 approach maximum deflection, in response to movement of pedal 10, as resistance of carbon pile 15 approaches its minimum. Further movement of pedal 10 causes leg 33 to completely deflect, and the free end 21 of contact 19 to engage contact 17 to establish the bypass path for maximum speed operation of the controlled motor (not shown).

Upon reduction of pressure on pedal 10, the sequence of operation of the components of the controller is reversed.

Contacts 17 and 19 and actuator 30 are stamped or cut from sheet metal and then formed and thus are reduced to their simplest single leaf spring form to substantially eliminate malfunction and wear normally attendant with assemblies of movable actuating parts. Further stated, a carbon pile resistor is provided with an actuator for varying the pressure applied to the carbon pile and vary the resistance derived therefrom as a function of deflection of the actuator. Although but two embodiments of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may also be made in the design and arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

Having thus described the nature of the invention, what we claim herein is:

1. A controller for electric motors, comprising:

(a) aninsulatingbase;

(b) a single carbon pile resistor supported on the base;

(c) a fiat sheet metal leaf spring actuator formed with a single elongated leg portion disposed parallel to and laterally offset from said pile resistor and lying in a first plane;

((1) means securing one end of said leg portion to said base;

(e) means at the other end of said leg portion providing a portion bent towards the base and lying in a second plane transverse to the first plane;

(f) means securing the free end of the transversely bent portion to said base;

(g) the bent portion being formed with an oflset pressure portion in contact with one end of the pile resistor for applying pressure thereto;

(h) single means engaging and deflecting the single leg portion to vary the pressure applied by the pressure portion to the pile resistor and to vary the resistance thereof;

(i) contact means engaging the end of the pile resistor opposite from the pressure portion of the actuator providing an electrical connection to the resistor; and

(j a contact supported by the base in normally spaced relation to the actuator and contacted by the leg portion when initially deflected to provide another electrical connection to the pile resistor.

2. A controller in accordance with claim 1 wherein the actuator including the pressure portion is formed from a single piece of sheet metal.

3. A controller in accordance with claim 1 wherein the leg portion and the bent portion of the actuator are formed from a single piece of sheet metal and the pressure portion is formed from a separate piece secured to the bent portion.

References Cited UNITED STATES PATENTS 2,371,772 3/1945 Naul 338108 2,384,772 9/1945 Schenk 338-108 2,536,012 12/1950 Turner 338-108 2,561,556 7/1951 Bell 338-108 2,620,419 12/ 1952 Sharenow et a1 338-108 2,988,720 6/1961 Voorlas 338-113 RICHARD M. WOOD, Primary Examiner. W. D. BROOKS, Assistant Examiner. 

1. A CONTROLLER FOR ELECTRIC MOTORS, COMPRISING: (A) AN INSULATING BASE; (B) A SINGLE CARBON PILE RESISTOR SUPPORTED ON THE BASE; (C) A FLAT SHEET METAL LEAF SPRING ACTUATOR FORMED WITH A SINGLE ELONGATED LEG PORTION DISPOSED PARALLEL TO AND LATERALLY OFFSET FROM SAID PILE RESISTOR AND LYING IN A FIRST PLANE; (D) MEANS SECURING ONE END OF SAID LEG PORTION TO SAID BASE; (E) MEANS AT THE OTHER END OF SAID LEG PORTION PROVIDING A PORTION BENT TOWARDS THE BASE AND LYING IN A SECOND PLANE TRANSVERSE TO THE FIRST PLANE; (F) MEANS SECURING THE FREE END OF THE TRANSVERSELY BENT PORTION TO SAID BASE; (G) THE BENT PORTION BEING FORMED WITH AN OFFSET PRESSURE PORTION IN CONTACT WITH ONE END OF THE PILE RESISTOR FOR APPLYING PRESSURE THERETO; (H) SINGLE MEANS ENGAGING AND DEFLECTING THE SINGLE LEG PORTION TO VARY THE PRESSURE APPLIED BY THE PRESSURE PORTION TO THE PILE RESISTOR AND TO VARY THE RESISTANCE THEREOF; (I) CONTACT MEANS ENGAGING THE END OF THE PILE RESISTOR OPPOSITE FROM THE PRESSURE PORTION OF THE ACTUATOR PROVIDING AN ELECTRICAL CONNECTION TO THE RESISTOR; AND (J) A CONTACT SUPPORTED BY THE BASE IN NORMALLY SPACED RELATION TO THE ACTUATOR AND CONTACTED BY THE LEG PORTION WHEN INITIALLY DEFLECTED TO PROVIDE ANOTHER ELECTRICAL CONNECTION TO THE PILE RESISTOR. 